1. Field of the Invention
The present invention relates to a testing method of a wafer provided with thin-film magnetic heads, and to a manufacturing method of a thin-film magnetic head using the testing method of the wafer.
2. Description of the Related Art
A recent thin-film magnetic head, particularly a recent inductive write head element has a quite fine and complicated structure. For example, a pole of the write head element has an elongated or slender shape and is subjected to influences of various processes such as etching process or resist-removal process after formation thereof because a magnetic shield layer for preventing blur in writing magnetic field will be formed around this pole. Thus, in the recent thin-film magnetic heads, defects such as a breakage or a disconnection of the pole are easy to come to occur, and it is required to certainly detect such a defect during a wafer process and to remove the thin-film magnetic heads having the defect.
As a conventional method of detecting defect in each thin-film magnetic head during the wafer process, there is an optical inspection method using a SEM (scanning electron microscope). However, because this inspection method using the SEM bases upon visual observation, discovering of a defect in each thin-film magnetic head itself is difficult and also great deal of time is required. For example, it may be necessary thirty seconds or more to check only one thin-film magnetic head and therefore several hundred hours to check all of the thin-film magnetic heads on the wafer. Thus, it was impossible to perform inspection for all of the thin-film magnetic heads fabricated to maintain quality of shipped thin-film magnetic heads well.
US 2008/100960 (Kakehi et al) discloses an insulation characteristic monitoring method of measuring whether insulation is ensured between layers of thin-film magnetic head elements formed on a wafer. This method uses a specific insulation-monitor element formed as a part of a large number of magnetic head elements on a wafer. An insulation characteristic between specially insulated layers in the insulation-monitor element is measured to infer the insulation characteristics of the general magnetic head elements from analogy.
However, because the insulation characteristics monitoring method described in Kakehi et al only checks whether there is insufficient insulation namely a short circuit or not, it is impossible to discriminate whether there is a defective in the head such as a breakage or disconnection of the magnetic pole. Further, because this insulation characteristics monitoring method checks the specific insulation-monitor element only but does not check all of the general magnetic head elements at all, it is difficult to increase reliability of the monitoring.
JP 6-333213A (Umemoto et al) discloses a method of testing a withstand voltage between an upper pole layer and a coil layer of each thin-film magnetic head formed on a wafer.
However, the withstand voltage test method described in Umemoto et al only detects whether a heavy-current flows or not to discriminate that there is no insulation tolerance and this thin-film magnetic head is defective when the heavy-current flows. Thus, this method cannot discriminate whether there is a defective in the head such as a breakage or disconnection of the magnetic pole at all.